Migration is an energetically expensive and hazardous stage of the annual cycle of non‐resident avian species, and requires certain morphological adaptations. Wing shape is one of the morphological traits that is expected to be evolutionarily shaped by migration. Aerodynamic theory predicts that long‐distance migrants should have more pointed wings with distal primaries relatively longer than proximal primaries, an arrangement that minimizes induced drag and wing inertia, but this prediction has mostly been tested in passerine species. We applied the comparative method of phylogenetically independent contrasts to assess convergent evolution between wing shape and migration within shorebirds. We confirmed the assumption that long‐distance migrants have less rounded wings than species migrating shorter distances. Furthermore, wing roundedness negatively correlates with fat load and mean distance of migratory flights, the basic components of migration strategies. After controlling for interspecific differences in body size, we found no support for a link between wing length and migration, indicating that wing shape is a more important predictor of shorebird migratory behaviour than wing length. The results suggest that total migration distance and migratory strategy may simultaneously act on the evolution of wing shape in shorebirds, and possibly in other avian species.
In most of colonial avian species, central parts of the colonies offer higher safety in terms of predatory pressure. However, in heterogeneous habitats, nest sites of high physical quality are likely to offer effective protection against predators or adverse weather conditions regardless of their location within the colony. The aim of this paper was to investigate whether nest site selection in a treenesting waterbird, the Great Cormorant Phalacrocorax carbo sinensis, depends on the within-colony location of sites, their physical quality or a combination of these components. The study was conducted during 2010-2011 in a cormorant colony in central Poland. We found that early-breeding individuals preferred nest sites in the central parts of the colony and located high off the ground. The high quality of pairs nesting in these locations was confirmed with good body condition of nestlings, measured by their body masses and plasma concentrations of glucose and urea. A similar spatial pattern was found for the daily nest survival rate and reproductive success. It was found that the central nesting sites associated with high nesting densities were better protected against predators, while the physical quality of nesting sites determined the probability of nest collapse before the conclusion of breeding activities. The two-way process of assessing nest site attractiveness (nest site location vs. physical quality) suggests that, under the limitation of the most attractive nesting sites (good-quality central sites), tree-nesting waterbirds may trade central nesting locations for the high-quality sites at the peripheries of the colony.
The relative ratio of the two main leukocyte types, heterophils (H) and lymphocytes (L), is known to change proportionally to the concentrations of stress hormones in the circulating blood. Thus, analysis of leukocyte profiles serves as a reliable proxy of stress in vertebrates, as high H/L ratios indicate stronger stress response. Moult and migration are among the most energetically demanding and nutritionally stressful processes in the annual cycle of wild birds. Although most birds separate these two activities in time, a moult-migration overlap has been reported for several avian species. The aim of this study was to examine whether overlapping energy requirements of moult and migration produce an increased organismal stress in a shorebird species, the Common Snipe (Gallinago gallinago). For this purpose, we assessed leukocyte profiles and nutritional condition in more than 350 moulting and non-moulting snipe during autumn migration through central Europe. We found negative correlations between H/L ratios and different measures of condition, including size-corrected body mass, fat load, and plasma concentrations of triglycerides and total protein. However, no evidence was found for the effect of moult status on H/L ratios. Our study indicates that while migration in a poor nutritional state can be associated with elevated stress response, the process of feather replacement may not constitute a serious stress for migrating Common Snipe. We suggest that these results may help to explain the occurrence of moult-migration overlap in the Common Snipe and possibly in other avian species.
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